Coordinate Measuring Apparatus And Method For Measuring An Object

ABSTRACT

The invention relates to a coordinate measuring apparatus ( 110 ) for measuring an object ( 3 ), comprising an x-ray sensory mechanism as a first sensory mechanism that is provided with an x-ray source ( 10 ) and at least one x-ray sensor ( 7 ) which detects the x-rays, and a second sensory mechanism such as a tactile and/or an optical sensory mechanism ( 8, 11; 9 ) that can be placed in the x, y, and/or z direction of the coordinate measuring apparatus in relation to the object. In order to be able to easily measure also large-size test objects, the x-ray sensory mechanism ( 7, 10 ) can be positioned in the coordinate measuring apparatus ( 10 ) according to the second sensory mechanism ( 8, 11; 9 ).

The invention relates to a coordinate measuring device for measuring anobject with an x-ray sensor system as the first part of the sensorsystem comprising an x-ray source, at least one x-ray sensor to measurethe x-rays, and a shield against x-ray radiation; and a second sensorsystem, such as a tactile and/or optical sensor system, which can bepositioned relative to the object along the x-, y- and/or z-axes of thecoordinate measuring device. The invention also relates to a method formeasuring an object comprising a coordinate measuring device with atleast one x-ray sensor system as well as a method for calibrating thex-ray sensor system.

The use of coordinate measuring devices with various sensors formeasuring the geometry of workpieces is known. These sensors aredescribed as optical and tactile sensors (DE.Z: Die Bibliothek derTechnik, Vol. 248). The use of computer-tomographs in determiningworkpiece geometry, particularly defects, is also known. DE-A-103 31 419describes a combination of both of these devices. In this particularcase, a computer-tomograph is fixedly secured to the basic assembly ofthe coordinate measuring device. Using classic coordinate measuringmachine-sensor technology, the position of the object of measurement isdetermined and subsequently positioned in the measurement range of thecomputer-tomograph.

The described prior art does not deal with several problems. Forexample, the problem of an object of measurement potentially exceedingthe measurement range of the computer-tomograph has not been solved.Because this component is fixedly secured to the basic assembly of thecoordinate measuring device, a composite image made up of severalcomputer-tomography images is not possible.

Furthermore, computer-tomographs usually have relatively grossmeasurement uncertainty in the magnitude of 10 μm or above. Measuring anobject of measurement with computer-tomography alone—as described inDE-A 103 31 419—is therefore not sufficient for the complete solution ofgeometrical measuring tasks involving conventional customized parts. Anadditional problem is the geometric calibration of computer-tomographs.Because the characteristics of tomographic measurement strongly dependon the characteristics of the measuring object itself, calibration ispossible only by means of a difficult and comprehensive procedureinvolving measurement standards.

From DE-A-100 44 169, a method for determining the thickness ofworkpieces is known. In this example, the x-rays penetrating a componentto be measured strike a detector. With the aid of a manipulator, thecomponent can be turned as well as raised and lowered. Following thecomplete transillumination of the component, the computer of acomputer-tomograph transmits a batch of grayscale sectional images,which are then assembled to create a three-dimensional voxel-dataset.The wall thickness of the component is then calculated from thisinformation.

DE-C-38 06 686 describes a coordinate measuring device with amultisensor sensing system that comprises a tactilely functioningsensor, a laser sensor and a video sensor, wherein one of the sensors isselected according to the measuring task. EP-A-1 389 263 proposesreplacing one of these sensors with a computer-tomograph.

Whenever x-ray sensor systems are used, comprehensive safety measuresfor shielding against x-ray radiation are necessary for compliance withradiation protection regulations. It must be ensured that the radiationexposure does not exceed the threshold prescribed for the measuringapparatus. A commonly known approach to meeting these requirements is toarrange around the measuring apparatus, hence independently thereof aradiation protection housing that is made of lead or lead-coatedcomposite material. The radiation protection housing has the exclusivetask of absorbing the x-ray radiation emitted by the computer-tomograph.The additional housing adds to the volume of the total measuringapparatus. This in turn results in an undesirable increase in weight aswell as high cost.

A further disadvantage of computer-tomographs of the prior art is thatthe measuring speed remains below that which coordinate measuringtechnology can achieve with optical sensors. Another disadvantage is thefact that the computer-tomograph is fixedly secured to the basicassembly of the coordinate measuring device, which in turn limits therange of measuring applications that can be performed.

US-A-2003/0043964 discloses an inspection system for airplane fuselagesthat comprises an x-ray source that works from a crane and is positionedinside the fuselage as well as a sensor that works from a crane and ispositioned outside the fuselage. Triangulation is employed to determinethe position of the sensor.

A measuring device described in DE-A-100 01 239 features a positiondetector, along with a non-optical measuring system such as an AFM(atomic force microscope), which are fixedly connected to one another bya bearing element.

A multi-sensor measuring head disclosed in DE-A-44 45 331 comprises avertical axis on which a plurality of sensors can be mounted.

In a coordinate measuring device described in EP-A-0 504 609,articulated milling heads are employed in addition to measuring heads.

An x-ray testing apparatus described in U.S. Pat. No. 5,038,378 providesthe possibility of adjusting x-ray detectors independently of each otheralong three axes.

The goal of the present invention is to further develop a method and acoordinate measuring device for measuring an object with at least onex-ray sensor system as its first sensor system, as well as a secondsensor system in the form of a tactile and/or an optical sensor system,so that objects of measurement of greater size can be measured withoutdifficulty. Additionally, an increased degree of measurement accuracycompared to that of the prior art should be achieved. Furthermore, itshould be possible to perform a geometric calibration of the x-raysensor system (computer-tomograph) by following a simple set ofinstructions. The apparatus should be of compact construction, while, atthe same time, sufficient shielding against x-rays should be ensured.High measurement densities and high measuring speeds should beachievable through simple means. Furthermore, improved resolution and areduction of signal-to-noise ratio should be facilitated. It should bepossible to perform sufficiently precise measurement of objects thatyield low contrast when subjected to x-rays.

To solve one aspect of the invention, a coordinate measurement device isproposed for measuring an object with an x-ray sensor system, the firstpart of the sensor system comprising an x-ray source and at least onex-ray sensor that measures the x-ray radiation, as well as a secondsensor system, such as a tactile and/or optical sensor system that canbe positioned relative to the object along the x-, y- and/or z-axes ofthe coordinate measuring device. The proposed system is distinguished bythe fact that the x-ray sensor system corresponding to the second sensorsystem can be positioned within the coordinate measuring device. Inother words, the x-ray sensor system equivalent to the second sensorsystem is arranged inside the coordinate measuring device, while, inprinciple, the positioning of x-ray sensor systems and the analyzing oftheir data can be managed by the same components or hardware andsoftware, which, in principle, can also be employed for any additionalsensors. The second sensor system can in turn comprise more than onesensor.

The invention therefore proposes, among other things, that the x-raysensor system (computer-tomograph) is not fixedly attached to thecoordinate measuring device, but rather that it is fully integrated intothe coordinate measuring device as a sensor system. The senders andreceivers of the computer-tomograph are also arranged in the coordinatemeasuring device in a configuration that is conventional intransillumination and image-processing sensor technology. X-rayreceivers and image-processing sensor or mechanical probes can bemovably arranged on a common mechanical axis. It is equally possible toemploy a separate axis for each sensor. The respective radiation sourcesfor visible light radiation and x-rays are arranged opposite theirrespective sensors.

By means of the inventive setup, it is possible to sequentially capturemultiple sections of the object of measurement through the known processof tomography (rotating the part and taking multiple x-ray images). Theentire collection of assembled x-ray images can then be used to generatea 3D-construction. The size of the objects that can be measured isthereby not limited to the visual field of the tomograph.

According to the invention, multiple tomographic images are arranged insequence using the coordinate measuring device or the coordinate systemof the measuring device.

It is also possible to measure those features of an object ofmeasurement that require more precise measurement in a traditionalmanner by using the sensors of the multi-sensor-coordinate measuringdevice (e.g. for tactile-optical measurement). X-ray sensors andimage-processing sensors and tactile sensors perform measurements usinga common coordinate system, as is conventional practice formulti-sensor-coordinate measuring devices. This allows the measurementresults to be related directly to one another.

With the given setup, it is now possible to perform the calibration ofthe measurements with the x-ray sensor system directly on the object ofmeasurement itself using the principle of tomography. Marked points onthe measuring object are measured with the tactile or optical sensorsystem of the coordinate measuring device at a known level of precision.These points are factored into the analysis of the computation of the3D-reconstruction of the computer-tomograph to facilitate the geometriccalibration of this reconstruction process.

To ensure sufficient shielding against x-ray radiation when a compactsetup is employed, the invention proposes, among other things, that theshielding or at least an area thereof be designed as a functionalcomponent of the required measurement technology setup of the coordinatemeasuring device. This component can, for example, be the housing of themechanical axis or the axis itself, base plates, supports etc., providedthis does not have a negative impact on the invention. In other words,the shielding necessary for radiation protection is taken overcompletely or in part by functional components of the measurementtechnology setup of the coordinate measuring device.

In particular, it is possible that the base plate and at least the rearwall of the housing of the coordinate measuring system are made to acertain thickness or manufactured of a certain material so that they canprovide the required shielding. The base plate or a side wall can alsobe designed in this way. In particular, it is proposed that thecomponents relevant for the shielding be composed of hard stone such asgranite. It is also possible to use other materials, particularlyartificial stone, which, if necessary, are treated with an appropriateradiation-absorbing material.

In a further development of the invention, the shielding or, as the casemay be, the components of the coordinate measuring device such as wallsthat form the shielding, can be the mounting site for functionalcomponents of the coordinate measuring device. Accordingly,shield-forming components can be used at the same time for the assemblyof functional components of the coordinate measuring device, inparticular the computer tomograph to be employed, where the functionalcomponents can be mechanical axes or traveling axes and/or sensorsand/or radiation or light sources.

To ensure sufficient shielding, the components used for the shieldingcan be of thickness greater than that required for measurementtechnology or static use.

According to one inventive proposal, several sensors are assigned to thex-ray source, the differing irradiation angles of the sensors crossingin the object, while, particularly for measuring an object, n-sensorssimultaneously struck by x-rays are assigned to the x-ray source, thex-ray source can be adjusted between consecutively performedmeasurements relative to the object at a base angle α and sensorsarranged one after the other can each be rotated in relation to theneighboring sensor by an angle α/n.

The inventive arrangement comprises n detectors for the x-rays, whichare arranged so that with each detector or sensor an x-ray image istaken at a different irradiation angle, whereby a decrease of therequired angular position for generating a tomogram is necessary.

According to the invention, the x-ray sensors are adjusted in relationto one another by an angular difference that is calculated as follows. Abase angle is used that is a whole-number multiple of the angular stepused between the radiation source and the sensor on one hand and theobject to be measured on the other hand, where the object is on arotating table, particularly one that can be rotated in relation to thex-rays sensor system. The angle of the second sensor is increased by avalue of 1/(number of sensors), while the angle of the third sensor isincreased by a value of 2/(number of sensors). Accordingly, the n^(th)sensor is increased by (n−1) /(number of sensors). For a singlerevolution, it is thus possible to ascertain the u-times number ofangular positions, where u=the product of n (the number of sensors) andm (the number of times the object is positioned in relation to the x-raysensor system).

According to the invention, the x-ray sensors are adjusted in relationto one another by a whole number multiple of the angular step of therotating table, while the irradiation time can be decreased for eachangular position. Regardless of this, the plurality of x-rays iscaptured by the plurality of sensors, thereby reducing thesignal-to-noise ratio.

An inventive embodiment provides that in the process of image taking or,as the case may be, image transmission or image evaluation, multiplepixel elements of the sensors are combined into one pixel and theoriginal resolution in the volume image, which is computed from theimages with correspondingly reduced pixel count, is achieved or exceededthrough mathematical interpolation.

After 2D-images are taken by means of tomography, the existing 2D-imagecan be converted into a lower resolution image with less pixelinformation through, for example, averaging of neighboring pixels. Usingthese lower resolution images, 3D-reconstruction is then performed togenerate a three-dimensional voxel image from the different 2D x-rayimages. After this voxel image is defined, the voxel-image is computedback into an image of the original resolution through interpolationbetween multiple voxels. It is even possible to calculate additionalvoxels through further application of the same approach using certainalgorithms, thereby achieving a higher resolution voxel image.

Also inventive is the idea that the object is continuously rotatedduring measurement, while the x-ray source is only briefly openedmultiple times with the aid of a mechanical or electronic shutter, forexample, or other measures that produce the same effect such ashigh-frequency modulation to prevent motion artifacts. Regardless ofthis, shortened measuring time is achieved in this manner.

Another embodiment also provides for multiple tomograms to be generatedfrom the object through the use of various spectral ranges of thex-rays. The spectral range of the x-rays is determined by the cathodevoltage of the x-ray generator. Typically—but purely as an example—theobject of measurement could be tomographically imaged with a cathodevoltage of 50 kV and 90 kV and 130 kV. Then, on the basis of thedifferences in measurement results at the different cathode voltages,specifically x-ray color or x-ray frequency, the magnitude of systematicmeasurement deviations, such as, for example artifacts, can beascertained and then corrected.

Multiple tomograms can also be taken of an object, while the anglebetween rotation axis of the rotating table holding the object and x-raysource and attached sensors can be varied among various angle settingswith the aid of mechanical rotational swivel axes or through the use ofmultiple detectors, while the sensors extend in particular along astraight line running parallel to the rotation axis of the rotatingtable.

To increase the resolution of the tomogram, multiple images can betaken, while, in the intervals between images, the sensor or the objectis shifted by a distance that is smaller than an edge length of asensitive element of the sensor.

The invention also proposes that the object be penetrated by parallelrunning x-rays. The x-rays are parallelized with the aid of suitabledevices.

Additionally or alternatively, it is also possible, with the aid oftranslatory relative movements between the object to be measured and thex-ray source/sensor, to image an area that is larger than the surfacearea of the sensor.

In order to image workpieces that exhibit only low contrast to x-rays,the invention proposes that the object be enveloped by a material thatfeatures higher absorption than the object itself. In the case of anobject of measurement made of a material with low mass number, such aslithium, the contrast of the tomographically obtained 2D-x-ray imagescan be improved by coating the object of measurement with a heaviermaterial. Images of sufficiently high contrast are thus obtained fromthe negative form of the object of measurement and in turn facilitate arepresentation of the object of measurement.

To achieve optimal measurement, different kinds of sensors can be usedin the measurement process. It is proposed that in addition to the x-raysource and the sensors attached thereto, additional sensors for themeasurement of the object such as mechanical probes, laser probes andimage-processing sensors are provided in the setup and, if necessary,are arranged on separate traveling axes.

The rotation axis facilitating the rotation of an object necessary fortaking a tomogram can be arranged on a traveling axis, whereby themeasurement area is expanded in the direction of the rotation axis. Inother words, the object can be adjusted in the direction of the rotationaxis.

An inventive proposal for calibrating the x-ray sensor system in thecoordinate measuring device provides that marked points of the object tobe measured are measured with a tactile and/or optical sensor system toascertain geometrical features such as diameter or distance, which arethen used for the calibration of the x-ray sensor system after the samegeometrical features have been ascertained with the x-ray sensor system.

The measurement results obtained through tactile and/or optic sensorsystems for marked points such as peripheral areas of the measurementvolume can thus be implemented in the correction of the measurementpoint cloud generated from the 3D-voxel-data by means of thethresholding.

The thresholding operation employed following tomography generates3D-point clouds, which can be represented in ASCI-format or STL-format.This point cloud is adjusted between the tactilely or opticallyascertained measurement point in such a way that the deviations betweentactile and/or optical measurement and the tomographic measurement arekept to a minimum. An interpolation is performed between the tactileand/or optical measurement points to determine the deviation.

When the voxel is calculated by means of 3D-reconstruction, thepositions of the voxel, which are located on the material margins (edgesof the measurement volume) of the object imaged through tomography, areadjusted by the correction value ascertained through tactile or opticalcounter measurement. Voxel positions between control points are thencorrected through interpolation between the measured correctionpositions. An irregular voxel raster in three-dimensional space ishereby generated, with the voxel locations corresponding more to theactual object geometry than to the original voxel image. Thisvoxel-image is then advantageously resampled in a regular raster. Thiscan be achieved by prescribing a target raster for the voxel image andby generating a new voxel amplitude from the voxel surroundingvoxel-amplitudes through interpolation for each point of the targetraster.

To achieve a high degree of measurement certainty and to facilitate ageometrical calibration of the x-ray sensor system (computer-tomograph)in a simple manner, the invention proposes that the positions for x-raysource and x-ray detector be stored with the appropriate calibrationdata for specific magnification and measurement range devices followinga single calibration and that they can be called up for subsequentmeasurements as desired through software without any furtherrecalibration.

In other words, the invention provides that all adjustment parametersnecessary for tomography at a certain magnification or a certainmeasurement range—this includes the position of the various axes of thetomography or coordinate measuring device—as well as the magnificationvalues and other calibration data assigned to these positions includingcorrection values for positioning the axis in relation to the positionmeasurement delivered by the connected displacement measurement systemsare recorded in a single calibration procedure of the coordinatemeasuring device and stored. In normal operation of the coordinatemeasuring device, these stored values are then called up by the user atthe touch of a button or by a CNC-program, the machine is moved into theappropriate positions and the appropriate calibration data is then usedin the subsequent measuring process.

It is provided in particular that previously calibrated magnificationand measurement range settings are automatically called up by themeasurement program of the coordinate measuring device and thecorresponding hardware components of the device are positioned.

It is also possible to have the x-ray source and the x-ray detectorsynchronously driven to change only the magnification and/or measurementrange or to move the x-ray source and the x-ray detector independentlyof one another to change the magnification and/or measurement range.

It is also possible to have all settings necessary for radiographicmeasurement (tomography) calibrated and stored in advance, so that foreach radiographic measurement procedure, such as a tomography procedure,calibration procedures are no longer necessary.

Adjustment of the rotation center can be realized through a calibrationprocedure and/or a corresponding correction of the rotation center driftin the software.

In another embodiment, the magnification for the tomography and/or theposition of the rotation center in relation to the x-ray source andx-ray detector is determined using a standard that consists of at leasttwo spheres. In this particular case, the standard consists of fourspheres.

A method for determining the position of the rotation center in acoordinate measuring device is distinguished in particular by thefollowing steps:

-   -   A four-sphere standard consisting of four spheres arranged at        the corners of a rectangle such as a square, wherein the spacing        of the spheres in relation to one another is known or        calibrated, is positioned on the rotation axis,    -   the four-sphere standard is rotated so that the mounted plane is        parallel to the detector,    -   Measurement of the four-sphere position in the measuring field        of the detector,    -   Calculation of the average magnification M1 from the four        measured sphere distances, the nominal sphere distances and the        nominal pixel size of the detector,    -   Rotation of the rotation axis by 180°,    -   Measurement of the four sphere positions in the image,    -   Calculation of the average magnification M2 from the four        measured sphere distances, the nominal sphere distances and the        nominal pixel size of the detector.

The Y-position of the rotation center is calculated from the four spherepositions prior to and following the rotation using the followingformula: Pdyn=(Pkyn1*M2+Pkyn2*M1)/(M1+M2) with Pdyn being the Y-positionof the rotation axis on the detector for sphere n, Pdy1 being theY-position of the sphere n at a rotation angle 0°, Pkyn 2 being theY-position of the sphere n at a rotation angle 180°, M1 being theaverage magnification at a rotation angle 0° and M2 being the averagemagnification at a rotation angle 180°.

It is also possible to measure an object using a coordinate measuringdevice that features other sensors in addition to x-ray sensor systems(computer-tomographs), allowing the measurements to be performed bymeans of a tactile or optical sensor system, with tactile-opticalmeasurements being mentioned in particular. It is thus possible to havethe measurement point cloud of the object of measurement measured withan x-ray sensor system or tomography or the triangulated surface elementcalculated from this data corrected through tactilely or opticallyobtained measurement points, while values can be interpolated betweenthe tactilely or optically measured correction points.

Values can also be interpolated between correction points obtained withtactile and/or optical sensor systems while factoring in the functionalcourse of the point cloud obtained through an x-ray measurementprocedure such as tomography and/or while taking into consideration thenominal CAD-model.

For the measurement of repetitive parts, another proposal provides thata sample part of the type of object of measurement is scanned usingx-rays (tomographically) as well as tactilely and/or optically, acorrection network for the correction of the tomographic measurementvalues is calculated from the difference of both measurements and thetomographic measurements are corrected with the correction valuesobtained one time.

This approach can be understood as involving a first measurementprocedure, in which many measurement points of a typical representativeof the object of measurement are tomographically and tactilely oroptically measured using x-rays. In this case, a great many measurementpoints are used, also in tactile and/or optical measuring, to achieve asufficiently dense correction network. From this data, correspondingcorrection values, which result from the comparison of the tactileand/or optical measurement values with the tomographic measurementvalues, are then determined for each surface position of the object thatundergoes tomography. When additional parts later undergo tomography,these correction values are directly applied. It is not necessary toperform another tactile or optical counter measurement.

For the measurement of repetitive parts, it is accordingly provided thata calibrated portion of an object of measurement undergoes tomography,that a correction network for the correction of tomographic measurementvalues is calculated from the measurement deviation occurring duringmeasurement, and the tomographic measurements are adjusted with thepreviously calibrated correction values.

When repetitive parts are measured, individual correction points,optically and/or tactilely measured, can also be factored in.

For correction, the tactile and/or optical measurement points can begraphically plotted by an operator on the point cloud generated bytomography and can then be measured automatically by the coordinatemeasuring device.

In another configuration, the tactile and/or optical measurement pointsfor correction are graphically plotted by an operator on the CAD-modelof the part to be measured and are then automatically measured by thecoordinate measuring device. The tactile and/or optical measurementpoints for correction, evenly or nearly evenly distributed by anautomatic algorithm on the surface of the CAD-model of the part to bemeasured, are automatically measured by the coordinate measuring device.The tactile and/or optical measurement points for correction can begraphically plotted on the CAD-model by an operator and, after theCAD-model has been loaded, can be automatically measured by thecoordinate measuring device.

The invention also teaches that in tomography procedures, a calibrationbody, in particular an arrangement of spheres, is in principle imagedthrough tomography, thereby allowing the relative position of therotation axis in relation to the coordinate measuring device and/or tothe x-ray source and/or to the x-ray sensor to be determined and thenmathematically corrected. Using this means, the position of thecalibration bodies on the rotation axis can be ascertained with opticaland/or tactile sensors and used for correction of the position of therotation axis.

It is also provided, in particular, that the calibration body, as wellas the minimum of two calibration spheres in the holding device, whichis the rotating table of the object to be measured, are incorporatedinto a material with low absorption of x-rays. The object of measurementcan thus be positioned on the rotating table through the detection ofthe calibration body, since the position of the center of rotation, andhence the rotation axis of the rotating table, can be ascertained usingthe calibration body.

According to the invention, the spatial location of the rotation axis inrelation to the x-ray source and x-ray detector can be ascertained withthe x-ray sensor system and/or with the tactile sensor system and/orwith the optical sensor system, and this deviation in position can bemathematically corrected when objects of measurement undergo tomography.

In particular, the position of the rotation axis deviating from thenominal position can be corrected through rotation and/or translationand/or distortion of the 2D-single images.

Furthermore, the position of the rotation axis deviating from thenominal position can be factored into the reconstruction algorithm.

Another proposal of the invention provides that the position of theobject of measurement on the rotating table, and thus in the machinecoordinate system, is ascertained using tactile and/or optical sensorsand/or tomography and then measured in 2D-x-ray mode at calibratedposition of the x-ray sensor on the basis of mass through methods ofimage processing.

These measures illustrate an additional operational principle of theinventive coordinate measuring device in which an x-ray sensor system isintegrated. The possibility of measuring in 2D-x-ray images is thusachieved. Conventionally this is not possible, as the actualmagnification on the object of measurement is not known. This is thecase because the position of the object of measurement in the x-rayspath is not known, and position, according to Thale's theorem,essentially determines magnification. If the position of the object ofmeasurement in the coordinate measurement device is precisely determinedwith an optical and/or tactile sensor system, the magnification of thecurrently irradiated object of measurement is known on the basis of thisposition and the use of an x-ray sensor system for two-dimensionalmeasurement with methods of image-processing is thereby possible.

The x-ray detector can be automatically controlled via thedevice-software, so that the detector is positioned in the radiationcone of the x-ray source during the actual tomography procedure and, atother times, is brought into parked position outside the radiation cone.

Through these measures, the amount of radiation to which the x-raysensor is exposed is minimized, thereby extending the life of thiscomponent.

The invention also provides for the image-processing sensor system andthe x-ray sensor system of a multi-sensor coordinate measuring device tobe outfitted with the same image-processing-hardware and the sameimage-processing-software or parts thereof The image processing methodsknown from image-processing sensor technology can also be used for anx-ray sensor system.

The invention also provides that prior to reconstruction, the 2D x-rayimages undergo distortion correction and/or bright signal correctionand/or dark signal correction and/or mathematical translation and/ormathematical rotation and/or a resampling process and/or linearitycharacteristic line correction and/or image processing filtering.

Preferred embodiments of the invention are described in both the claimsand subclaims.

Additional details, advantages and features of the invention can befound not only in the claims and the features detailed therein,individually and/or in combination, but also from the followingdescription of the preferred embodiment illustrated in the drawings.

Shown are:

FIG. 1 a schematic diagram of a multi-sensor coordinate measuring device

FIG. 2 a functional diagram of a 3D-computer tomograph

FIG. 3 an additional schematic diagram of a coordinate measuring device

FIG. 4 a schematic diagram of a first arrangement of x-ray source andassigned sensors

FIG. 5 a schematic diagram of a second arrangement of x-ray source andassigned sensors

FIG. 6 a schematic diagram for image evaluation

FIG. 7 a schematic diagram for illustrating a process for increasing theresolution of a tomogram

FIG. 8 a schematic diagram of a calibration body

FIG. 9 a schematic diagram of a rotating table with a calibration body

FIG. 10 a block diagram and

FIG. 11 a conceptual diagram to illustrate a correction process.

FIG. 1 is a schematic diagram of a coordinate measuring device for thecombined use of an x-ray sensor system and an optical and tactile sensorsystem, even if the invention is essentially suited for features of acoordinate measuring device that comprises no additional sensor systembeyond the computer-tomograph.

Arranged on an axis 18 running parallel to the X-axis is a rotatingtable 2. Present thereon is an object of measurement 3, which can thusbe rotated on a rotation axis 18 and displaced by the axis 18 in thedirection X (double arrow). Arranged on a slide 4 running parallel tothe Y-axis are two axes 5, 6 running parallel to the Z-axis. Located onthe mechanical axis 5 is a sensor 7 for x-rays and an image-processingsensor 8. Additionally located on the mechanical axis 6 is a tactilesensor 9. Arranged opposite the x-ray sensor 7 is an x-ray source 10,which can be mounted either movably in the direction of Y or fixedly asdesired. Opposite the image-processing sensor system 8 is a transmittedlight source 11. The mechanical axes and slide, which run along the X-,Y- and Z- axes of the coordinate measuring device, are designed so thatsensors installed in or on the coordinate measuring device can eachcover the entire measurement range on the rotating table 2.

The integration of computed-tomography (CT) into a multi-sensorcoordinate measuring device creates entirely new possibilities. A quick,nondestructive complete measurement with tomography is combined withhigh-precision measurements of functional dimensions with tactile oroptical sensor system. The invention provides that the x-ray sensorsystem (sensor, radiation source) corresponding to the second sensorsystem (e.g. image-processing sensor, transmitted light beam source orincident light beam source or tactile sensor, if necessary with attachedimage-processing sensor) can be positioned in the coordinate measuringdevice so that the x-ray sensor system is arranged equally with thesecond sensor system. The x-ray sensor system can be arranged with atleast the tactile sensor system and/or the optical sensor system on acommon mechanical axis or on a separate mechanic axis that functionsanalogously to the mechanical axes for the tactile and/or optical sensorsystem.

The functional principle of 3D-computed tomography is illustrated usingFIG. 2. The reference numbers for the elements shown in FIG. 1 areretained.

The workpiece 3 is disposed on a rotating table 2 and transilluminatedwith x-rays. The sensor 7, shown here for example in the form of asurface detector, converts the x-ray image into a digital 2D-image forfurther processing. The object 3 is turned 360° and x-ray images aretaken in multiple rotational positions. The 2D-images are then used fora 3D-reconstruction of measurement points that describes the entireworkpiece geometry to be measured. Through the integration of one ormore of the additional sensors 8, 9 the range of applications of thecomputer-tomograph can be expanded. The image-processing sensor 8 allowsthe fully automatic measurement of complicated, extremely low-contrastworkpieces in transmitted light and incident light. Tactile sensingsystems facilitate high-precision measurements of optically inaccessiblefeatures.

It is also possible to adjust the sensor 7 and the x-ray source 10synchronously to the object, that is, with their distance to one anotherremaining the same. This allows an adaptation of measurement range,which, if necessary, can be automatic. Alternatively, the object 3 canbe shifted in relation to the sensor 7 to facilitate an adaptation tothe workpiece size and the precision requirements. If the object 3 isshifted toward the sensor 7, lower magnification is achieved, whereas ifthe object 3 is shifted toward the x-ray source 10, a greatermagnification can be achieved. If a stationary x-ray source 10 is used,the sensor can also be shifted toward the object 3.

The invention offers the following particular advantages:

-   -   Complete detection of all fixed and free form geometries of a        workpiece in a single measurement procedure,    -   Measuring interior geometries and inaccessible features (e.g.        obscured edges, undercuts),    -   High precision measurement of functional dimensions with tactile        or optical sensor system,    -   Recirculation of tomographic measurement results through        multisensor technology,    -   Combine measuring with tomography and other sensors in a        measurement cycle    -   2D- and 3D- measurements of form, dimensions and position,    -   Comprehensive functions for 2D-measurement in x-ray images,    -   3D-target-actual comparison as 3D- deviation display in        comparison with 3D-CAD-model,    -   Generation of 3D-CAD-data from acquired CT-data.

FIG. 6 illustrates an additional method characterizing the inventionthat facilitates a compression of data without sacrificing resolution.In fact, the corresponding teachings even make it possible to surpassthe original resolution. This is explained using a 2D-image.

In FIG. 6 the squares represent the pixels of a 2D-image. The present2D-image is converted into a lower resolution image with less pixelinformation (pixels illustrated as crosses) through, for example,averaging the neighboring pixels. From corresponding 2D x-ray images oflower resolution a 3D-reconstruction for computing the three-dimensionalimage is then performed. After this voxel image has been defined, thevoxel-image, which in the 2D-illustration shown in FIG. 6 is alsosimulated through crosses, is then computed back into an image of theoriginal resolution through interpolation between multiple voxel images,so that an image with squares—also shown as a 2D-illustration—isyielded. Using the same approach, it is also possible to computeadditional voxels to achieve a higher resolution of the voxel image.This is symbolized with circles.

In this way, computation can be performed faster, because a lowerresolution can be used at first without requiring resolution to besacrificed in the end. In fact, resolution can even be surpassed.

Using FIG. 7 for reference, a further inventive method is examined thatallows the resolution in the tomogram to be increased. To achieve thisend, multiple shots are taken, while during the intervals between shots,the sensor is shifted in relation to the object or the object is shiftedin relation to the sensor by a distance that is smaller than the edgelength of a sensitive element of the sensor. In FIG. 7 the resolution ofthe x-ray detector (sensor) employed is illustrated by pixels drawn assquares. During the process of tomography, for each rotational position,an image is taken in the position of the x-ray detector represented as asquare along with an image taken in the position of the x-ray detectorrepresented as a circle with an X, along with one in the position of thex-ray detector represented as a circle with a Y, along with one in theposition of the x-ray detector represented as a circle with a Z. Allimages are assembled to form an image and are recognized as singleentity during the tomography reconstruction process. A higher resolutionis thereby achieved than is physically provided by the detector.

To determine the magnification for the tomography and/or the rotationcenter of the rotating table 2 in FIG. 1 in relation to the x-ray source10 or the sensor 7, a standard can be used, which in the embodimentillustrated in FIG. 8, is labeled 50. In the schematic diagram, abearing element 54 made of a material with low x-ray absorption extendsfrom a stand 52. Arranged in the bearing element 54 are at least twospheres 56, 58 of a material with high x-ray absorption, such as steel.The standard 50 is then arranged on a tomograph rotating table 60, whichcorresponds to the rotating table 2 from FIG. 1. The rotating table 60can be rotated on an axis 62, which overlaps the X-axis of thecoordinate measuring device. The measurement procedure for determiningthe position of the rotation axis 62 of the tomograph within thecoordinate measuring device is now determined through measuring theposition of the spheres 56, 68 relative to the x-ray sensor in variousrotational positions of the sphere standard 50.

If the magnification level is to be ascertained, then it is necessary totake measurements at two different distances from the sensor 7.

To facilitate a high degree of precision, the standard 50 can featuretwo additional spheres 64, 66.

Below it is described how the distance between the x-ray source 10 andthe sensor 7 is determined by means of a standard, which in theembodiment consists of a four-sphere standard comprising four spheresarranged at the corners of a square.

-   -   The distances among the spheres are known (calibrated).    -   The four-sphere standard is arranged on the rotation axis.    -   The four-sphere standard is rotated so that the mounted plane is        parallel to the detector.    -   Measurement of the four sphere positions in the image at        position Z1    -   Calculation of the average magnification M1 from the four        measured distances among the spheres,    -   the nominal distances among the spheres and the nominal pixel        size of the detector    -   Driving the rotation axis in the direction of the source (or        source and detector perpendicular to the rotation axis)    -   Measurement of the four sphere positions in the image at        position Z2    -   Calculation of the average magnification M2 from the four        measured distances among the spheres,    -   the nominal distances among the spheres and the nominal pixel        size of the detector    -   Calculation of the distance between source and detector using        the following equation:

AQD=dZ*M1*M2/(M2−M2)

where:

-   -   AQD: Distance source-detector    -   M1: Magnification at position Z1    -   M2: Magnification at position Z2    -   dZ: Distance between position Z1 and Z2    -   Calculation of the distance from source to Z1 using the        following equation

D1=dZ*M2/(M1−M2)

-   -   Calculation of the distance from source to Z2 using the        following equation

D2=D1+dZ=dZ*M1/(M1+M2)

-   -   Calculation of the position of the cone axis on the detector        using the following equation

Pd=(Pkn1*D1−Pkn2*D2)/dZ

-   -   where:    -   Pd: Deviation vector of the cone axis-position from the center        of the detector    -   Pkn1: Position vector of the sphere n on the detector at        position Z1    -   Pkn2: Position vector of the sphere n on the detector at        position Z2    -   Calculation of the average deviation vector from the four        deviation vectors for each sphere position

A method for determining the Y-position of the rotation axis center,also while using a four-sphere standard comprising four spheres arrangedat the corners of a square, proceeds as follows:

-   -   The distances among the spheres are known (calibrated).    -   The four-sphere standard is arranged on the rotation axis.    -   The four-sphere standard is rotated so that the clamped plane is        parallel to the detector.    -   Measurement of the four sphere positions in the image    -   Calculation of the average magnification M1 from the four        measured distances among the spheres,    -   the nominal distances among the spheres and the nominal pixel        size of the detector    -   Rotating the rotation axis by 180°    -   Measurement of the four sphere positions in the image    -   Calculation of the average magnification M2 from the four        measured distances among the spheres,    -   the nominal distances among the spheres and the nominal pixel        size of the detector    -   Calculation of the Y position of the center of rotation from the        four sphere positions prior to and following the rotation using        the following equation:

Pdyn=(Pkyn1*M2+Pkyn2*M1)/(M1*M2)

-   -   where:    -   Pdyn: Y position of the rotation axis on the detector for sphere        n    -   Pkyn1: Y position of the sphere n at rotation angle 0°    -   Pkyn2: Y position of the sphere n at rotation angle 180°    -   M1: Average magnification at rotation angle 0°    -   M2: Average magnification at rotation angle 180°

Further inventive features of the invention can be seen in FIG. 3 to 5.FIG. 3 represents a purely schematic diagram of a coordinate measuringdevice 110 with a housing 112, which comprises a base plate 114, a rearwall 116, side walls 118, 120 as well as a top wall 122, which can alsobe identified as a cover plate.

The x-axis, y-axis and z-axis of the coordinate measuring device arelabeled in the drawing with the reference numbers 124, 126 and 128. Onthe inside 130 of the rear wall 116 of the housing 112 a guide runs inthe direction X, adjustably mounted along which, hence running in thedirection X 124, is a mounting 132 for a rotating table 134, on whichthe object 136 to be measured is arranged. In other words, the rotatingtable 134 is arranged on the x-axis 124.

Running along the y-axis 126 are guides, along which a housing 138 canbe displaced. Projecting from the housing 138 is a mounting 140 that isdisplaceable along the z-axis 128.

Furthermore, projecting from the base plate 114 is an x-ray source 142,the x-rays of which penetrate the object 136 arranged on the rotatingtable 134. The x-rays are captured by suitable sensors such as CCDsensors that are sensitive to x-rays.

Furthermore, sensors 144 can project from the z-axis 128, specificallyfrom the mounting 140 in the embodiment. The sensors here can be thosethat are conventional for coordinate measuring devices, hence, forexample, tactile or optical sensors. Thus not only tomography can beperformed, but tactile or optical measurements can also be made withimage-processing sensors, laser distance sensors etc.

Due to the use of x-rays, it is required that the coordinate measurementdevice 110 be provided with sufficient shielding to prevent outwardescape. In this regard the invention proposes that at least several ofthe weight-bearing components provide a shielding function. For example,the base plate 114 and/or the rear wall 116 can be dimensioned ordesigned to ensure the required shielding function.

At the same time, the corresponding walls 114, 116 thereby provide afunction that is required for the measurement technology assembly,namely a guide for the x- and y-axes in the embodiment.

It is also possible to provide walls that do not feature a sufficientshielding effect with radiation absorbing layers 146 on the insideand/or the outside. In this particular case, lead sheeting is involved.

With regard to the weight-bearing walls, in particular those providing ashielding function, the use of hard stone such as granite or appropriatematerials is preferred. Also conceivable for use is an artificial hardstone such as polymer concrete, which can be treated withx-ray-absorbing material such as magnetite or similar to the degreerequired.

According to the invention, the housing 112 of the coordinate measuringdevice or parts thereof perform a double function, namely that of therequired shielding as well as that of serving as functional componentsof the measurement technology assembly. This results in a compactconstruction.

To allow high measurement density or to facilitate only short radiationexposure times at each measurement position without sacrificingmeasurement accuracy, it is provided according to FIG. 4 that multipletomograms are taken simultaneously—thus in each measurement position ofthe object 136—at different irradiation angles. In FIG. 4 projectingfrom the base plate 114 is the rotating table 134 as is shown in FIG. 3,on which an object (not shown) to be measured is arranged, which isirradiated by x-radiation 150 emanating from a x-ray generator 148. Inthe embodiment, the radiation is captured by a total of three x-raysensors 152, 154, 156, so that three tomograms for different irradiationdirections in a single measurement position of the object are yielded.In each measurement position, hence each angular position of therotating table 34, the sensors 152, 154, 156 are read out and projectionimages for the tomogram are acquired. The angular position of thesensors 152, 154, 156 is designed in such a way that each angle betweenthe sensors 152, 154, 156 differs by a whole number multiple of therotating table 136 angular step used in operating the computertomograph, while the second and third sensor 154, 156 are arranged asrotated by one third of the angular step in relation to the first sensor152 and the second sensor 154, respectively.

To take more tomograms of the object 136 to be measured, where the anglebetween the rotation axis 158 of the rotating table 154 and thex-radiation 150 is visibly changed, three sensors 160, 162 164 arearranged, for example, at different angles to the main irradiationdirection of the x-ray source 148 in the embodiment shown in FIG. 5,whereby the visible deviation of the x-rays source in relation to therotation axis 158 is simulated.

The double arrow 166 drawn in FIG. 5 is intended to symbolize that therotating table 134 can be adjusted along the rotation axis 158 parallelto the X-axis.

FIG. 9 schematically illustrates that, during the process of tomography,a calibration body, preferably in the form of spheres 300, 302, can, inprinciple, be tomographically imaged at the same time, thereby yieldingthe relative position of the rotation axis 158 of the rotating table 134on which the object 136 to be measured is arranged. The spheres 300, 302can be arranged in a housing 304 of low x-ray absorption, whereas thespheres 300, 302 are highly absorbent and are made of steel, forexample. During the process of tomography, the position of the rotationaxis 158 in relation to the coordinate measuring device or to the x-raysource 10 or to the sensor 7 can be determined without any problemsbefore then being mathematically corrected.

According to the invention, measurement points on the object ofmeasurement are gathered with a tactile and/or optical sensor system andused in the correction of the measurement points gathered with the x-raysensor system. This is should become clear from FIG. 11, whichillustrates the principle of a corresponding correction procedure. FIG.11 shows an object of measurement 400 that is measured tactilely andoptically at selected points. In this example, corresponding measurementpoints are labeled with the reference numbers 402, 404, 406. In theprocess of tomographic imaging, which is performed subsequently in thesame coordinate measuring device, the form, as changed through typicalerrors of tomography, appears in the tomographic point cloud 408. Thiscan be due to typical tomography artifacts, for example. The positionsof the tomographic measurement points are corrected on the basis of theavailable measurement points measured more precisely with optical and/ortactile sensor system and illustrated once again in FIG. 11 b.Interpolation can be performed between the tactilely and opticallymeasured measurement points. The result obtained is then a geometricallycorrected tomographically measured point cloud 410 that bettercorresponds to the form of the object of measurement 400 than does theoriginal data of the tomogram. This point is illustrated through acomparison of 11 b and 11 c.

During the processes of performing the measurements and analyzing themeasurement results, the image-processing sensor system for measuringthe visible light in the transmitted light method—if necessary also inthe incident light method—can be coupled to the same image processingevaluation unit or the same image processing board as the x-ray sensorsystem. Driven by software, it is then possible to switch between bothof the sensors and digitalize and compute in the same hardware. This isconceptually illustrated in FIG. 10, in which an image-processing sensorsystem 500 and an x-ray sensor system 502 are connected to the sameimage processing board 502 so that they may function in the mannerdescribed above.

1-105. (canceled)
 106. Coordinate measuring device (110) for measuringan object (3, 136) with an x-ray sensor system as a first sensor systemcomprising an x-ray source (10) and at least one x-ray sensor (7)capturing the x-rays as well as a second sensor system such as a tactileand/or optical sensor system (8,11; 9), which can be positioned relativeto the object in x-, y- and/or z- direction, characterized by the factthat the x-ray sensor system (7,10) is adapted to be positioned in thecoordinate measuring device (10) corresponding to the second sensorsystem (8,11; 9).
 107. A coordinate measuring device according to claim106, wherein the x-ray sensor system (7,10) is arranged equally with thesecond sensor system (8,11; 9).
 108. A coordinate measuring deviceaccording to claim 106, wherein the x-ray sensor system (7,10) isarranged on a common mechanical axis (5,6) with at least the tactilesensor system and/or the optical sensor system (8,11).
 109. A coordinatemeasuring device according to claim 106, wherein the x-ray sensor system(7, 10) is arranged on a separate mechanical axis, which functionsanalogously as the mechanical axes (5, 6) do for the tactile and/oroptical sensor system (8,11;9).
 110. A coordinate measuring deviceaccording to claim 106, wherein both the x-ray sensor system (7,10) andthe second sensor system (8,11; 9) cover a common measurement volume ofthe object (3,136).
 111. A coordinate measuring device according toclaim 106, wherein the coordinate measuring device (110) is equippedwith at least a rotation axis (18; x-axis direction) perpendicular tothe functional direction (y- and/or z-axis direction) of the x-raysensor system (7,10) and/or the optical sensor system such as animage-processing sensor (8, 11) and/or the tactile sensor system (9).112. A coordinate measuring device according to claim 111, wherein therotation axis (18, 158) rotates on a vertically running axis (x-axis).113. A coordinate measuring device according to claim 106, wherein theoptical axis for the optical sensor (9) and/or the ray axis for thex-ray sensor (8) is horizontal and/or perpendicular to the rotation axis(18, 138; x-axis).
 114. A coordinate measuring device according to claim106, wherein radiation or a light source (10, 11) for the x-ray sensorsystem and/or the image-processing sensor system can be movedsynchronously with the assigned sensor (7, 8).
 115. A coordinatemeasuring device according to claim 106, wherein the radiation source(10) for the x-ray sensor system is fixedly arranged in the coordinatesystem of the coordinate measuring device (110).
 116. A coordinatemeasuring device according to claim 106, wherein both the x-ray sensorsystem (7, 10) and the second sensor system (8, 10; 9) can bepositionally adjusted in relation to the object (3, 136) along at leastone axis.
 117. A coordinate measuring device according to claim 106,wherein both the x-ray sensor system (7, 10) and the second sensorsystem (8, 10; 9) can be positionally adjusted in relation to the object(3, 136) along at least two axes.
 118. A coordinate measuring deviceaccording to claim 106, wherein both the x-ray sensor system (7, 10) andthe second sensor system (8, 10; 9) can be positionally adjusted inrelation to the workpiece (3, 136) along at least three axes.
 119. Acoordinate measuring device according to claim 106, wherein at least oneadditional sensor (8) is arranged so that it can be adjustedsynchronously with the x-ray sensor system (7, 10).
 120. A coordinatemeasuring device according to claim 106, wherein a measurement areaadaptation is achieved preferably automatically by adjusting thedistance between the x-ray sensor (7) and the radiation source (10)and/or by adjusting the x-ray sensor system (7, 10) relative to theobject (3).
 121. A coordinate measuring device according to claim 106,wherein shielding (114, 116, 118) against x-rays, or at least a portionthereof, is designed as a functional component for the requiredmeasurement technology setup of the coordinate measuring device (110).122. A coordinate measuring device according to claim 121, wherein abase plate (114) and/or at least one side or rear wall (116, 118) of thecoordinate measuring device is designed as shielding.
 123. A coordinatemeasuring device according to claim 121, wherein the components (114,116) required for the shielding are designed to be made of stone such asgranite.
 124. A coordinate measuring device according to claim 121,wherein the shielding or components forming this part, such as baseplate (114) or rear or side walls (116, 118), are the mounting site forone or more functional components such as e.g. a mechanical axis of thecoordinate measuring device (110).
 125. A coordinate measuring deviceaccording to claim 106, wherein the shielding (114, 116) is the mountingsite or area for at least one mechanical axis or, as the case may be, atraveling axis and/or mounting and/or guide for an element such as asensor (144) and/or a mounting or guide for a radiation or light source(142) as the functional component.
 126. A coordinate measuring deviceaccording to claim 106, wherein assigned to the x-ray source (142, 148)is a plurality of sensors (152, 154, 156), wherein the irradiationangles of the sensors penetrating the object deviate from one another.127. A coordinate measuring device according to claim 106, wherein forthe measuring of the object, n-sensors (152, 154, 156) simultaneouslystruck by x-rays are assigned to the x-ray source (148), that the x-raysource can be adjusted between consecutively performed measurementsrelative to the object at a base angle α, and that sensors arranged oneafter the other each are aligned twisted or tilted relative to eachother at an angle α/n.
 128. A coordinate measuring device according toclaim 106, wherein the arrangement features a plurality of sensors (152,154, 156, 160, 162, 164) detecting the x-rays (150), which are arrangedso that for each sensor an x-ray image of the object (136) can be takenat a different irradiation angle.
 129. A coordinate measuring deviceaccording to claim 106, wherein tomograms of the object (136) can beobtained by employing different spectral ranges of the x-rays (150).130. A coordinate measuring device according to claim 106, wherein inthe process of image taking or, as the case may be, image transmissionor image evaluation, multiple pixel elements of the sensors can becombined in each case into one pixel and the original resolution in thevolume image, which is computed from the images with correspondinglyreduced pixel count, is achieved or surpassed through mathematicalinterpolation.
 131. A coordinate measuring device according to claim106, wherein during measurement the object (136) can be continuouslyrotated and can be discontinuously exposed to x-rays.
 132. A coordinatemeasuring device according to claim 106, wherein a mechanical and/orelectronic shutter is assigned to an outlet of the x-ray source (148).133. A coordinate measuring device according to claim 106, wherein thex-radiation (150) can be modulated high frequently.
 134. A coordinatemeasuring device according to claim 106, wherein several sensors (160,162, 164) are arranged along a straight line running parallel to therotation axis (58) of the object (36) and are arranged in relation tothe projection axis of the x-ray source (48) at angles deviating fromone another.
 135. A coordinate measuring device according to claim 106,wherein an object exhibiting low contrast relative to x-rays (150) issurrounded or encased by a material with an x-ray absorption greaterthan that of the object.
 136. A coordinate measuring device according toclaim 106, wherein the arrangement features, in addition to the sensors(152, 154, 156, 160, 162, 164) capturing the x-radiation (150), furthercomprise sensors for measuring technical detection of the object (136),such as mechanical probe, laser probe, image-processing sensor.
 137. Acoordinate measuring device according to claim 106, wherein some of thesensors are arranged on separate traveling or mechanical axes.
 138. Acoordinate measuring device according to claim 106, wherein the rotationaxis (18) of the object (3) is arranged on a traveling axis (1) for thepurpose of expanding the measurement range along the rotation axis. 139.A coordinate measuring device according to claim 106, wherein the object(136) is arranged on a rotating table rotatable around the rotating axis(158), that arranged in the rotating table or in an element immediatelyconnected thereto, is a calibration body, preferably in the form of twocalibration spheres (300, 302), which is arranged in a material thatfeatures lower x-ray absorption than the calibration body itself.
 140. Acoordinate measuring device according to claim 106, wherein theimage-processing sensor system (500) for the measuring with visiblelight is connected to the same image processing evaluation unit or thesame image processing board (504) as the x-ray sensor system (502). 141.A method for calibrating an x-ray sensor system in a coordinatemeasuring device as defined in claim 106, wherein marked points of theobject to be measured are measured with a tactile or optical sensorsystem, and that geometrical features such as diameter or distances arethereby ascertained, which are then used for calibrating the x-raysensor system after the same geometric features have been ascertainedwith the x-ray sensor system.
 142. A method according to claim 141,wherein the measurement results obtained through tactile and/or opticsensor systems for marked points are implemented in the correction ofthe measurement point cloud generated from the 3D-voxel-data by means ofthe thresholding, wherein said data is obtained through measurementperformed with x-ray sensor systems (tomography).
 143. A methodaccording to claim 141, wherein measurement results obtained for themarked points through tactile and/or optical sensor systems are used asearly as the computation of the 3D-reconstruction of the x-ray(tomography) procedure.
 144. A method according to claim 141, whereinmeasurement points alternatively ascertained with tactile sensorsystems, optical sensor systems or x-ray sensor systems are analyzed ina common coordinate system.
 145. A method according to claim 141,wherein the geometrical features such as diameter and spacing arecalculated from points measured by a combination of x-ray sensorsystems, optical sensor systems or tactile sensor systems.
 146. A methodaccording to claim 141, wherein from the measurement points obtainedwith x-ray sensor technology and/or from the tactilely obtainedmeasurement points and/or from the optically obtained measurement pointsa common point cloud for further analysis is generated.
 147. A methodfor measuring an object by means of a coordinate measuring devicecomprising an x-ray sensor system with an x-ray source, at least onex-ray sensor capturing x-rays as well as a shield against x-radiation asa first sensor system and a second sensor system such as a tactileand/or optical sensor system, which can be positioned relative to theobject along the x-, y- and/or z-direction of the coordinate measuringdevice, characterized by the fact that the x-ray sensor system in thesame manner as the second sensor system is positioned within thecoordinate measuring device.
 148. A method according to claim 147,wherein the x-ray sensor system is arranged equally with the secondsensor system.
 149. A method according to claim 147, wherein the x-raysensor system or its sensor is arranged on a common mechanical axis withat least the tactile sensor system or its sensor and/or the opticalsensor system or its sensor.
 150. A method according to claim 147,wherein the x-ray sensor system is arranged on a separate mechanicalaxis that functions analogously to the mechanical axes for the tactilesensor system and/or the optical sensor system.
 151. A method accordingto claim 147, wherein a common measurement volume is covered by thex-ray sensor system and the tactile sensor system and/or the opticalsensor system.
 152. A method according to claim 147, wherein thecoordinate measuring device is equipped with at least one axis (z-axis)perpendicular to the functional direction (x- and/or y-direction) of thex-ray sensor system and/or the optical sensor system such as animage-processing sensor and/or the tactile sensor system.
 153. A methodaccording to claim 147, wherein the rotation axis rotates on avertically running axis.
 154. A method according to claim 147, whereinthe functional or mechanical axis for the optical sensor system or thesensor thereof and/or the x-ray sensor system or the sensor thereof isaligned horizontal and/or perpendicular to the rotation axis.
 155. Amethod according to claim 147, wherein the radiation source for thex-ray sensor system and/or the image processing sensor system are movedsynchronously with the sensors assigned thereto.
 156. A method accordingto claim 147, wherein the radiation source for the x-ray sensor systemis fixedly arranged in the coordinate system of the coordinate measuringdevice.
 157. A method according to claim 147, wherein both the x-raysensor or the x-ray sensor system and the optical sensor or the opticalsensor system and/or the tactile sensor or the tactile sensor system arearranged adjustably in relation to the object on at least one axis. 158.A method according to claim 147, wherein both the x-ray sensor and theoptical sensor and/or the tactile sensor are arranged adjustably inrelation to the object on at least two axes.
 159. A method according toclaim 147, wherein both the x-ray sensor and the optical sensor and/orthe tactile sensor are arranged adjustably in relation to the object onat least three axes.
 160. A method according to claim 147, wherein atleast one additional sensor is arranged adjustably together with thex-ray sensor system.
 161. A method according to claim 147, wherein ameasurement area adaptation is achieved by adjusting the distancebetween the x-ray sensor system and the radiation source and/or byadjusting object and x-ray sensor system in relation to one another.162. A method for measuring structures and/or geometrical features of anobject such as a workpiece by means of a coordinate measuring devicewhile using an x-ray sensor system (computer-tomograph) comprising anx-ray source, at least one sensor capturing the x-rays as well as ashielding against x-rays, wherein during the process of measuring, thex-ray sensor system is rotated relative to the object, in particular theobject to the x-ray sensor system, characterized by the fact that atleast one functional component of the coordinate measuring device isdesigned as the shielding.
 163. A method according to claim 162, whereinthe shielding is designed as a mounting site for functional componentsof the coordinate measuring device, such as a traveling axis and/orsensor and/or radiation or light source.
 164. A method according toclaim 162, wherein a base plate of the coordinate measuring deviceand/or side wall and/or rear wall are designed as shielding.
 165. Amethod according to claim 162, wherein the functional components usedfor the shielding are of a thickness greater than that required formeasurement technology or static use.
 166. A method according to claim162, wherein multiple sensors are assigned to the x-ray source in such away that an x-ray image is taken by each sensor, where irradiationangles deviate from one another.
 167. A method according to claim 162,wherein tomograms are taken of the object using different spectralranges of the x-ray radiation.
 168. A method according to claim 162,wherein in the process of image taking or, as the case may be, imagetransmission or image evaluation, multiple pixel elements of theconverter are in each case combined into one pixel and the originalresolution in the volume image, which is computed from the images withcorrespondingly reduced pixel count, is achieved or surpassed throughmathematical interpolation.
 169. A method according to claim 162,wherein the object is continuously rotated during the measurements (datarecording), while the x-ray source is opened for only brief periods withthe aid of a mechanical or electrical shutter.
 170. A method accordingto claim 162, wherein during measurement, the object is continuouslyrotated and discontinuously exposed to x-rays.
 171. A method accordingto claim 162, wherein multiple images (tomograms) of the object aresimultaneously taken, where an angle between rotation axis of the objectand x-rays is varied with the aid of mechanical swivel axes or the useof multiple detectors at different angles.
 172. A method according toclaim 162, wherein for increasing the resolution of the tomogram,multiple images are taken, in the intervals between which the sensor orthe object is shifted by a distance that is smaller than edge length ofa sensitive element of the sensor.
 173. A method according to claim 162,wherein the x-rays are made parallel.
 174. A method according to claim162, wherein with the aid of translatory relative movement betweenobject and x-ray source or x-ray sensor, an area is taken that is largerthan sensor surface area.
 175. A method according to claim 162, whereinthe measurement of an object made of materials exhibiting low contrastto x-rays is performed in that the object is surrounded by a materialthe x-ray absorption of which being greater than that of the object.176. A method according to claim 162, wherein in addition to the sensoror sensors for capturing the x-radiation, additional sensors formeasuring technical detection of the object such as e.g. a mechanicalprobe, a laser probe and an image processing sensor are employed.
 177. Amethod according to claim 162, wherein at least a few of the sensors arearranged on separate traveling axes.
 178. A method according to claim162, wherein a rotation axis necessary for taking a tomogram and forrotating the object is arranged on a traveling axis for magnification ofthe measurement area in the direction of the rotation axis.
 179. Amethod for measuring an object with a coordinate measuring devicecontaining at least one x-ray sensor system with x-ray source and x-raydetector, characterized by the fact that the positions for x-ray sourceand x-ray detector can be stored with the appropriate calibration datafor specific magnification and measurement range arrangements followinga single calibration, and data stored in this manner can be used duringfollowing measurements with the x-ray sensor systems without any furtherrecalibration.
 180. A method according to claim 179, wherein previouslycalibrated magnification and measurement range settings areautomatically called up by the measurement program of the coordinatemeasuring device, and the corresponding hardware components of thedevice are positioned.
 181. A method according to claim 179, wherein thex-ray source and the x-ray detector are synchronously driven in order tochange only the magnification and/or measurement range.
 182. A methodaccording to claim 179, wherein the x-ray source and the x-ray detectorare driven independently of one another to change the magnificationand/or measurement range.
 183. A method according to claim 179, whereinall settings necessary for x-ray measurement (tomography measurements)are calibrated and stored in advance so that for each x-ray measurementprocedure, such as a tomography procedure, calibration procedures are nolonger necessary.
 184. A method according to claim 179, wherein theadjustment for the rotation center of the object can be realized througha calibration procedure and/or a corresponding correction of therotation center drift in the software.
 185. A method according to claim179, wherein the magnification for the tomography and/or the position ofthe rotation center in relation to the x-ray source and x-ray detectoris determined using a standard that consists of at least two spheres.186. A method according to claim 179, wherein the magnification for thex-ray measurement (tomography) and/or the position of the rotationcenter in relation to the x-ray source and x-ray detector is determinedusing a standard that consists of at least four spheres.
 187. A methodaccording to claim 179, wherein the steps for determining the positionof the rotation center in the coordinate measuring device comprise: afour-sphere standard consisting of four spheres arranged at the cornersof a rectangle such as a square, wherein the spacing of the spheres inrelation to one another is known or calibrated, is positioned on therotation axis, the four-sphere standard is rotated so that the definedplane is parallel to the detector, measurement of the four-sphereposition in the measuring field of the detector, calculation of theaverage magnification M1 from the four measured sphere distances, thenominal sphere distances and the nominal pixel size of the detector,rotation of the rotation axis by 180°, measurement of the four spherepositions in the image, calculation of the average magnification M2 fromthe four measured sphere distances, the nominal sphere distances and thenominal pixel size of the detector.
 188. A method according to claim179, wherein the Y-position of the rotation center is calculated fromthe four sphere positions prior to and following the rotation using thefollowing formula: Pdyn=(Pkyn1*M2+Pkyn2+M1)/(M1*M2) with Pdyn being theY-position of the rotation axis on the detector for sphere n, Pkyn1being the Y-position of the sphere n at a rotation angle 0°, Pkyn2 beingthe Y-position of the sphere n at a rotation angle 180°, M1 being theaverage magnification at a rotation angle 0° and M2 being the averagemagnification at a rotation angle 180°.
 189. A method according to claim179, wherein in the coordinate measuring device measurement pointsmeasured by means of tactile and/or optical sensor systems are used forthe correction of the measurement points obtained with the x-ray sensorsystem.
 190. A method according to claim 179, wherein the measurementpoint cloud of the object of measurement measured with the x-ray sensorsystem or tomography or the triangulated surface element calculated fromthis data is corrected through tactilely and/or optically obtainedmeasurement points.
 191. A method according to claim 190, wherein valuesare interpolated between the tactilely and/or optically measuredcorrection points.
 192. A method according to claim 191, wherein it isinterpolated between correction points obtained with a tactile and/oroptical sensor system while factoring in the functional course of thepoint cloud obtained through an x-ray measurement or, as the case maybe, tomography and/or while taking into consideration the nominalCAD-model.
 193. A method according to claim 183, wherein at first asample part of the type of object of measurement is scanned by x-rays(tomographically) as well as tactilely and/or optically, a correctionnetwork for the correction of the tomographic measurement values iscalculated from the difference of both measurements and, when repetitiveparts are measured, the tomographic measurements are corrected with theone-time defined correction values.
 194. A method according to claim179, wherein a calibrated portion of an object of measurement undergoestomography, that a correction network for the correction of tomographicmeasurement values is calculated from the measurement deviationoccurring during measurement and, when repetitive parts are measured,the tomographic measurements are adjusted with the previously calibratedcorrection values.
 195. A method according to claim 193, wherein whenrepetitive parts are measured, individual optically and/or tactilelymeasured correction points are additionally factored in.
 196. A methodaccording to claim 193, wherein for correction, the tactile and/oroptical measurement points are graphically plotted by an operator on thepoint cloud generated by tomography and are then measured automaticallyby the coordinate measuring device.
 197. A method according to claim193, wherein for correction, the tactile and/or optical measurementpoints are graphically plotted by an operator on the CAD-model of thepart to be measured and are then automatically measured by thecoordinate measuring device.
 198. A method according to claim 193,wherein the tactile and/or optical measurement points for correction arenearly evenly or evenly distributed on the surface of the CAD-model byan automatic algorithm and are automatically measured by the coordinatemeasuring device.
 199. A method according to claim 179, wherein thetactile and/or optical measurement points for correction are predefinedon the CAD-model by an operator and, after the CAD-model has beenloaded, are automatically measured by the coordinate measuring device.200. A method according to claim 179, wherein when a tomographyprocedure is performed, a calibration body, in particular, anarrangement of spheres, is also subjected to tomography, therebyallowing the relative position of the rotation axis in relation to thecoordinate measuring device and/or to the x-ray source and/or to thex-ray sensor and/or the effective magnification is determined and thenmathematically corrected.
 201. A method according to claim 200, whereinthe calibration body, in particular the calibration spheres, is placedin a carrier with lower radiation absorption properties than that of thecalibration body, while the object of measurement is positioned on arotating table, with the calibration body being taken intoconsideration.
 202. A method according to claim 179, wherein theposition of the calibration bodies on the rotation axis is determinedwith optical and/or tactile sensors and used for correction of theposition of the rotation axis.
 203. A method according to claim 179,wherein the spatial location of the rotation axis in relation to thex-ray source and x-ray detector is measurement-technically ascertainedwith the x-ray sensor system and/or with the tactile sensor systemand/or with the optical sensor system, and this deviation in position ismathematically corrected when objects of measurement undergo tomography.204. A method according to claim 179, wherein the position of therotation axis deviating from the nominal position is corrected throughrotation and/or translation and/or distortion of the 2D-single images.205. A method according to claim 179, wherein the position of therotation axis deviating from the nominal position is factored into thereconstruction algorithm.
 206. A method according to claim 179, whereinthe position of the object of measurement on the rotating table and thusin the machine coordinate system is ascertained using tactile and/oroptical sensors and/or tomography and then measured in 2D x-ray mode atcalibrated position of the x-ray sensor by scales using methods of imageprocessing.
 207. A method according to claim 179, wherein the x-raysensor or x-ray sensor system is automatically controlled via thedevice-software, while the x-ray sensor is positioned in the radiationcone of the x-ray source during the actual measurement (tomographyprocedure) and, at other times, is brought into parked position outsidethe radiation cone.
 208. A method according to claim 179, wherein theimage-processing sensor system and x-ray sensor system of a multisensorcoordinate measuring device are equipped with the same image-processinghardware and the same image-processing software or portions thereof.209. A method according to claim 179, wherein the image processingmethods known from image-processing sensor technology can also be usedfor the x-ray sensor system.
 210. A method according to claim 179,wherein prior to reconstruction, the 2D x-ray images undergo adistortion correction and/or a bright signal correction and/or a darksignal correction and/or a mathematical translation and/or amathematical rotation and/or a resampling process and/or a linearitycharacteristic line correction and/or an image processing filtering.